Performance optimization of a reservoir computing system based on a solitary semiconductor laser under electrical-message injection.

A simple reservoir computing (RC) system based on a solitary semiconductor laser under an electrical message injection is proposed, and the performances of the RC are numerically investigated. Considering the lack of memory capacity (MC) in such a system, some auxiliary methods are introduced to enhance the MC and optimize the performances for processing complex tasks. In the pre-existing method, the input information is the current input data combined with some past input data in a weighted sum in the input layer (named as M-input). Another auxiliary method (named as M-output) is proposed to introduce the output layer for optimizing the performances of the RC system. The simulated results demonstrate that the MC of the system can be improved after adopting the auxiliary methods, and the effectiveness under adopting the M-input integrated with the M-output (named as M-both) is the most significant. Furthermore, we analyze the system performances for processing the Santa Fe time series prediction task and the nonlinear channel equalization (NCE) task after adopting the above three auxiliary methods. Results show that the M-input is the most suitable for the prediction task while the M-both is the most appropriate for the NCE task.

Numerical simulations on narrow-linewidth photonic microwave generation based on a QD laser simultaneously subject to optical injection and optical feedback.

Based on a three-level model for quantum dot (QD) lasers, the characteristics of the photonic microwave generated by a QD laser simultaneously subject to optical injection and optical feedback are numerically investigated. First, the performance of the microwave signal generated by an optical injected QD laser operating at period one state are analyzed, and the mappings of the frequency and intensity of the generated microwave in the parameter space of the frequency detuning and injection strength are given, which are roughly similar to those reported experimentally. Next, an optical feedback loop is further introduced to the optically injected QD laser for compressing the linewidth of the microwave signal, and the results demonstrate that the linewidth of the generated microwave can be reduced by at least 1 order of magnitude under suitable feedback parameters. Finally, the effect of the linewidth enhancement factor on the generated microwave signal is analyzed.

Performance optimization research of reservoir computing system based on an optical feedback semiconductor laser under electrical information injection.

Via Santa Fe time series prediction and nonlinear channel equalization tasks, the performances of a reservoir computing (RC) system based on an optical feedback semiconductor laser (SL) under electrical information injection are numerically investigated. The simulated results show that the feedback delay time and strength seriously affect the performances of this RC system. By adopting a current-related optimized feedback delay time and strength, the RC can achieve a good performance for an SL biased within a wide region of 1.1-3.5 times its threshold. The prediction errors are smaller than 0.01 when implementing the Santa Fe tests, and the symbol error rates (SERs) are very low on the order of 10-5 for accomplishing nonlinear channel equalization tests under a signal-to-noise ratio (SNR) of 32 dB. Moreover, under a given RC performance level, the information processing rate of the RC can be improved by increasing the SL current.